This application claims the priority of German Patent Application, Serial No. 199 46 111.2, filed Sep. 17, 1999, the subject matter of which is incorporated herein by reference.
The present invention relates to a device for continuous chipless separation of identical rings from a tubular workpiece.
A device for the continuous chipless separation of single identical rings from tubular workpieces is described in International PCT patent application WO 95/29777 and includes three cutting rollers which are driven in a same direction and arranged around the tubular workpiece being worked on. The cutting rollers are interconnected through positive engagement and include a cylindrical basic body which has axial ends defining a slip bevel and a calibrating section, respectively, and a threaded section with thread-shaped cutting edges disposed between the slip bevel and the calibrating section. The cutting edges include, as viewed in longitudinal section, a pointed cutting head and a cutting foot with flanks that are oriented substantially perpendicular to the respective roller axis. The flanks have a width which increases from entry to exit. The contour in the base between the cutting edges of the cutting rollers is substantially parallel to the roller axis, and the diameter of each cutting roller increases from beginning toward the end. This conventional device suffers shortcomings because only in theory can it separate rings of an outer diameter of at most 80 mm and a width of at most 40 mm. In fact, as tests have shown, the limits of the device are already reached when separating rings that have an outer diameter of 65 mm and a width of 25 mm. Moreover, this device is not able to separate asymmetric rings.
It is thus an object of the present invention to provide an improved device for continuous chipless separation of identical rings from a tubular workpiece, obviating the afore-stated drawbacks.
In particular, it is an object of the present invention to provide an improved device for continuous chipless separation of identical rings from a tubular workpiece, which allows a separation of rings of greater outer diameter and greater width than previously possible.
It is still another object of the present invention to provide an improved device for continuous chipless separation of asymmetric rings from a tubular workpiece.
These objects, and others which will become apparent hereinafter, are attained in accordance with the present invention by providing at least two cutting rollers which are placed around the tubular workpiece and operate in a same direction and which are interconnected by a positive engagement, whereby each cutting roller includes a basic body having opposite axial ends defining an entry zone and an exit zone, respectively, with the basic body having a slip bevel at the entry zone, a calibrating section at the exit zone, and a cutting screw disposed between the slip bevel and the calibrating section and including a helical main thread portion with a conical entry part and a substantially cylindrical primary part in succession of the entry part, whereby the cutting screw has at least one further thread disposed between threads of the main thread portion of the cutting screw.
The arrangement of at least one additional thread between threads of the main thread portion of the cutting screw may be realized in the entry part or in the primary part. Suitably, when provided in the primary part, the at least one additional thread may have a configuration intended to profile the outer contour of the ring. An arrangement of at least one additional thread in the entry part improves gripping conditions for grabbing the tubular workpiece and reduces wear of the highly stressed threads, whereby the outer diameter of the additional thread is suitably equal or smaller than a diameter of the primary part, thereby ensuring that the lead of the main thread portion, which is determinative for the width of the ring, remains unchanged and effective. As soon as the tubular workpiece is fully grabbed, the additional thread is no longer required and may run out. Depending on the width and the diameter of the ring being separated, two or more additional threads may be provided.
According to another feature of the present invention, at least one additional thread may be formed in the entry part whereas still another further thread is formed in the primary part for profiling the outer contour of a ring being produced, whereby the additional thread in the entry part merges into the further thread in the primary part, suitably in the transition zone between the entry part and the primary part. Thus, in this fashion not only is the device capable to separate individual rings but the rings can also be provided with a symmetric or asymmetric outer profile. Optionally, the additional thread in the primary part may or may not adjoin a neighboring thread of the main thread portion of the cutting screw.
Evidently, the possibilities with respect to the addition of additional threads are infinite. For example, the additional thread in the primary part may be formed with a cutting thread so that not only the outer contour of the ring can be profiled but also the ring itself can be split into two halves to thereby produce two asymmetric inner rings. Other examples may include the provision of two or more additional threads in the entry part that merge into two or more additional threads in the primary part, respectively, or the provision of two or more additional threads in the entry part that merge into a single additional thread in the primary part.
With a device according to the present invention, larger and wider rings than was possible heretofore can now be processed in chipless fashion from a tubular workpiece, including the production of rings with an outer contour or even a split of a ring in two halves.